1. Field of the Invention
The present invention relates to an optical connector boot mounted to the forward end portion of an optical fiber cable inserted into and secured in a connector ferrule.
2. Description of the Related Art
An optical fiber cable tends to undergo an increase in radiation loss when its bending radius is reduced. Thus, when an optical fiber cable is inserted into and secured in a connector ferrule to assemble an optical connector, it is general practice to pass the forward end portion of the optical fiber cable through an optical connector boot mounted to the rear end portion of the connector ferrule so that the bending radius of the optical fiber cable may not become less than a predetermined value, thereby preventing the optical fiber cable from being bent.
In a known optical connector boot (commonly called a “direction changing boot”), the forward end portion of the optical fiber cable passed therethrough is gradually bent as it extends in the axial direction. FIG. 21 shows an example of this type of optical connector boot. The optical connector boot shown in FIG. 21 is equipped with an attachment portion A to be mounted to the rear end portion of a connector ferrule and a cable passing portion B which has a semi-arcuate sectional configuration and through which an optical fiber cable with a round sectional configuration (hereinafter referred to as a “round type optical fiber cable”) is passed. At one longitudinal end of the cable passing portion B, a retaining member C protrudes radially so as to lap the round type optical fiber cable passed through the cable passing portion B to thereby retain the cable within the cable passing portion B. Further, the cable passing portion B is curved gradually as it extends in the longitudinal direction. Provided in the attachment portion A is an outlet hole E communicating with the cable passing portion B and allowing the forward end portion of the optical fiber cable passed through the cable passing portion B to be drawn out.
Apart from a round type optical fiber cable as mentioned above, a flat type optical fiber cable with a flat section is also inserted into and secured in a connector ferrule. However, the connector boot shown in FIG. 21 is designed for a round type optical fiber cable and its cable passing portion B has a semi-arcuate sectional configuration as mentioned above. Thus, if a flat type optical fiber cable with a flat section is passed through the cable passing portion B of the connector boot shown in FIG. 21, the cable may be twisted or bent in an unexpected direction.
In a state in which an optical connector equipped with a connector boot is connected to the other connector or the like, application of a vertical or lateral tensile load to a flat type optical fiber cable inserted into the connector boot will cause the boot to be bent in the corresponding direction, with the flat type optical fiber cable therein also being bent in the same direction. In particular, when the flat type optical fiber cable is a multi-core optical fiber, application of a vertical tensile load to the flat type optical fiber cable will generate an abrupt twisting within a small range of the multi-core optical fiber, resulting in an increase in connection loss and a break in the cable.